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PRISM Manual | PropertySpecification / PropertiesFiles 
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    <p><a class='wikilink' href='Introduction.html'>Property Specification</a> /
</p><h1>Properties Files</h1>

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<h3>Constants</h3>
<p>Files containing properties to be analysed by PRISM can also contain constants, as is the case for model files.
These are defined in identical fashion, for example:
</p>
<div class='vspace'></div>
<div class='sourceblock ' id='sourceblock1'>
  <div class='sourceblocktext'><div class="prism"><span class="prismkeyword">const</span> <span class="prismkeyword">int</span> <span class="prismident">k</span> = <span class="prismnum">7</span>;<br/>
<span class="prismkeyword">const</span> <span class="prismkeyword">double</span> <span class="prismident">T</span> = <span class="prismnum">9.5</span>;<br/>
<span class="prismkeyword">const</span> <span class="prismkeyword">double</span> <span class="prismident">p</span> = <span class="prismnum">0.01</span>;<br/>
<br/>
<span class="prismkeyword">P</span>&lt;<span class="prismident">p</span> [ <span class="prismkeyword">F</span>&lt;=<span class="prismident">T</span> <span class="prismident">x</span>=<span class="prismident">k</span> ];<br/>
</div></div>
  <div class='sourceblocklink'><a href='PropertiesFiles@action=sourceblock&amp;num=1' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>As before, these constants can actually be left undefined and then later
assigned either a single value or a range of values using <a class='wikilink' href='../RunningPRISM/Experiments.html'>experiments</a>.
</p>
<p class='vspace'>In fact, values such as the probability bounds for the <code><strong>P</strong></code> or <code><strong>S</strong></code> operators (like <code><strong>P</strong></code> above)
and upper or lower bounds for the <code><strong>U</strong></code> operator (like <code> T</code> above)
can be arbitrary expressions, provided they are constant.
Furthermore, expressions in the properties file can also refer to constants previous defined in the model file.
</p>
<div class='vspace'></div><h3>Labels</h3>
<p>Another feature of properties files is <em>labels</em>. These are a way of defining sets of states that will be referred to in properties (they correspond to <em>atomic propositions</em> in a temporal logic setting). As described <a class='wikilink' href='../ThePRISMLanguage/FormulasAndLabels.html'>earlier</a>, labels can be defined in either model files or property files.
</p>
<p class='vspace'>Labels are defined using the keyword <code><strong>label</strong></code>, followed by a name (identifier) in double quotes, and then an expression which evaluates to a Boolean. Definition and usage of labels are illustrated in the following example:
</p>
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  <div class='sourceblocktext'><div class="prism"><span class="prismkeyword">label</span> "<span class="prismident">safe</span>" = <span class="prismident">temp</span>&lt;=<span class="prismnum">100</span> | <span class="prismident">alarm</span>=<span class="prismkeyword">true</span>;<br/>
<span class="prismkeyword">label</span> "<span class="prismident">fail</span>" = <span class="prismident">temp</span>&gt;<span class="prismnum">100</span> &amp; <span class="prismident">alarm</span>=<span class="prismkeyword">false</span>;<br/>
<br/>
<span class="prismkeyword">P</span>&gt;=<span class="prismnum">0.99</span> [ "<span class="prismident">safe</span>" <span class="prismkeyword">U</span> "<span class="prismident">fail</span>" ];<br/>
</div></div>
  <div class='sourceblocklink'><a href='PropertiesFiles@action=sourceblock&amp;num=2' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>Two special cases are the <code>"init"</code> and <code>"deadlock"</code> labels which are always defined.
These are true in initial states of the model and states where deadlocks were found (and fixed by adding self-loops), respectively.
</p>
<p class='vspace'><a name='names' id='names'></a>
</p><h3>Property names</h3>
<p>For convenience, properties can be annotated with <em>names</em>, as shown in the following example:
</p>
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<div class='sourceblock ' id='sourceblock3'>
  <div class='sourceblocktext'><div class="prism">"<span class="prismident">safe</span>": <span class="prismkeyword">P</span>&lt;<span class="prismnum">0.01</span> [ <span class="prismkeyword">F</span> <span class="prismident">temperature</span> &gt; <span class="prismident">t_max</span> ];<br/>
</div></div>
  <div class='sourceblocklink'><a href='PropertiesFiles@action=sourceblock&amp;num=3' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>which gives the name <code>"safe"</code> to the property. It is then possible to include named properties as sub-expressions of other properties, e.g.:
</p>
<div class='vspace'></div>
<div class='sourceblock ' id='sourceblock4'>
  <div class='sourceblocktext'><div class="prism"><span class="prismkeyword">filter</span>(<span class="prismident">forall</span>, <span class="prismident">num_sensors</span>&gt;<span class="prismnum">0</span> =&gt; "<span class="prismident">safe</span>");<br/>
</div></div>
  <div class='sourceblocklink'><a href='PropertiesFiles@action=sourceblock&amp;num=4' type='text/plain'>[&#036;[Get Code]]</a></div>
</div>

<p class='vspace'>Notice that the syntax for referring to named properties is identical to the syntax for labels. For this reason, property names must be disjoint from those of any existing labels.
</p>
<p class='vspace'>You can refer to property names when using the command-line switch <a class='wikilink' href='../RunningPRISM/ModelChecking.html#cl'><code>-prop</code></a> to specify which property is to be model checked.
</p>
<div class='vspace'></div><h3>Properties files</h3>
<p>A PRISM properties file can contain any number of properties.
It is good practice, as shown in the examples above, to terminate each property with a semicolon. Currently, this is not enforced by PRISM (to prevent incompatibility with old properties files) but this may change in the future.
</p>
<p class='vspace'>Like model files, properties can also include any amount of white space (spaces, tabs, new lines, etc.) and C-style comments, which are both ignored.
By convention, files are given the extension <code>.pctl</code> for properties of DTMCs, MDPs or PTAs
and extension <code>.csl</code> for properties of CTMCs.
</p>
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<h3><a class='wikilink' href='../Main/Welcome.html'>PRISM Manual</a></h3>
<p><strong><a class='wikilink' href='Introduction.html'>Property Specification</a></strong>
</p><ul><li><a class='wikilink' href='Introduction.html'>Introduction</a>
</li><li><a class='wikilink' href='IdentifyingASetOfStates.html'>Identifying A Set Of States</a>
</li><li><a class='wikilink' href='ThePOperator.html'>The P Operator</a>
</li><li><a class='wikilink' href='TheSOperator.html'>The S Operator</a>
</li><li><a class='wikilink' href='Reward-basedProperties.html'>Reward-based Properties</a>
</li><li><a class='wikilink' href='SyntaxAndSemantics.html'>Syntax And Semantics</a>
</li><li><a class='wikilink' href='Filters.html'>Filters</a>
</li><li><a class='wikilink' href='PTAProperties.html'>PTA Properties</a>
</li><li><a class='selflink' href='PropertiesFiles.html'>Properties Files</a>
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